I'm looking at the example sentences you have for もらえる and くれる。
When you added 私があなたに and あながが私に to those sentences, I felt like a lot of emphasis was placed on the people involved rather than the favor being asked. To me it sounds like 千円を貸してくれる? is a completely different question than あなたが、私に千円を貸してくれる? The first sounds like asking your friend if you can borrow some cash. The second one sounds like you have your mind set on borrowing cash, and asking if this particular person is going to be the one to give it to you. Similarily, 私が、あなたに千円を貸してもらえる？ sounds like asking if the speaker is going to be the one receiving money from the person giving.
I'm looking at the example
I'm looking at the example sentences you have for もらえる and くれる。
When you added 私があなたに and あながが私に to those sentences, I felt like a lot of emphasis was placed on the people involved rather than the favor being asked. To me it sounds like 千円を貸してくれる? is a completely different question than あなたが、私に千円を貸してくれる? The first sounds like asking your friend if you can borrow some cash. The second one sounds like you have your mind set on borrowing cash, and asking if this particular person is going to be the one to give it to you. Similarily, 私が、あなたに千円を貸してもらえる？ sounds like asking if the speaker is going to be the one receiving money from the person giving.